STRUCTURAL ELUCIDATION OF (SILICA)-O-RH(ALLYL)2 BY CORRELATED H-1 AND C-13 NMR

The combined rotation and multiple pulse sequence technique was used to obtain H-1 NMR spectra of (silica)-O-Rh(allyl)2, a reactive organometallic complex bound in low concentration on the surface of the oxide, and a model compound, [(eta3-allyl)2RhCl]2. By spectral comparison with the model compound, a bis(eta3-allyl)Rh structure seemed possible for the surface-bound complex, but broad line widths precluded a more definite structural assignment. The C-13-labeled complex (eta3-allyl)(eta3-[C-13]allYl)2Rh (in which either terminus of the allyl ligand was labeled) was prepared and deposited on silica. The resulting labeled surface complex was analyzed by both C-13 cross-polarization magic angle spinning and the 2D H-1-C-13 heteronuclear correlation technique. Spectral data were compared with those obtained for [(eta3-[C-13]allyl)2-RhCl]2 and support the bis(eta3-allyl)Rh complex structural assignment for (silica)-O-Rh(allyl)2.